In Death Note (TV Series 2006–2007), there is a pattern in a lot of the numeric references in the rules of the Death Note, where they relate to the number 4 in some way:
If the cause of death is written within the next 40 seconds of writing the person's name, it will happen.
After writing the cause of death, details of the death should be written in the next 6 minutes and 40 seconds [= 400 seconds total].
If a human uses the note, a god of death usually appears in front of him/her within 39 days [under 40 days] after he/she uses the note.
The Death Note will be rendered useless if the victim's name is misspelled four times.
If you lose the Death Note or have it stolen, you will lose its ownership unless you retrieve it within 490 days [a year and 4 months].
If writing the same name on more than two Death Notes is completed within a .6 seconds [0.4 seconds away from 1], it is regarded as simultaneous; the Death Note will not take effect and the individual written will not die.
Those with the eye power of the god of death will have the eyesight of over 3.6 [0.4 away from 4] in the human measurement, regardless of their original eyesight.
—"Rules of the Death Note", Death Note Wiki
There are a few instances where other significant numbers ("magical number" 3, and "devil number" 6) are used, but none are quite as prevalent as 4.
Is this prevalent pattern a coincidence, or is there some significance to the number 4 that would be relevant in Death Note?